5. The expression a[b+(c-d)] is equivalent to:
A. ab + ac - ad
B. ab + ac + ad
C. ab + ac - d
D. ab + c + d
E. ab + c - d
解析：The correct answer is A. To find an equivalent expression, multiply a by b+c-d. This results in a(b) + a(c) + a(-d), or ab + ac - ad.
正确答案选A。根据乘法分配率展开括号可得ab + ac - ad。
上一篇：托业考试词汇语法模拟试题14 下一篇：2013年雅思阅读模拟试题及答案解析3